The invention relates generally to a method and apparatus for providing heat exchanges between fluids. More particularly, the invention concerns a method and apparatus for transferring heat between diverse working fluid circuits in a manner having maximum reversibility and which is independent of characteristics of the transfer mode. The diverse working fluid circuits each circulate a fluid which may add or substract heat both while the fluid is maintained at a constant temperature, as for example in boilers or condensers, or while the fluid is undergoing a discrete temperature change, for example in circuits involving temperature dependent heat.
A heat-exchange process between fluids is already known in which a working fluid circuit receives heat from the latent heat of a low-pressure condensing vapor that is at an elevated temperature. Such a process and a heat-pump for implementation of the process are described in the applicant's French patent application No. 75 11.438. In the heat pump, a multi-stage compressor has an intake stage for a primary fluid which is in the form of a saturating vapor. Each stage of the compressor and its associated cell constitutes one module. The cells are arranged in series and communicate with each other through orifices which are calibrated at the level of the primary fluid condensate. A plurality of cooling-condensation heat exchange cores are located in a corresponding plurality of subsequent cells with the plurality of cores being associated at least with the highest pressure cells in the amount of one core per cell. In addition, means for introducing a secondary fluid into the first core of the plurality of cores is provided. Means is also provided for evacuating the secondary fluid from the core of the last cell associated with the highest pressure stage. Finally, means is provided for evacuating the primary fluid at the level of the first cell in the wholly liquid state.
Another heat exchange process is described in the applicant's French patent application No. 76 14.965 of May 18, 1976, entitled "Inter-Fluid Heat-Exchanging Process & Equipment." In this process, means is provided by which heat fed by a first fluid is used to change a second fluid from a liquid state to a saturated vapor state. The process of that invention is particularly applicable when low-level, temperature dependent heat is available in a liquid, for example a geothermal brine, and where it is desired to transfer the temperature dependent heat to another liquid such as fresh water by raising the temperature of the other liquid. In this process, if a liquid at temperature T.sub.1 is available, the temperature of the liquid is lowered to T.sub.o. The heat released during this reduction in temperature is used to heat another liquid from a temperature T.sub.2 to a temperature T.sub.3, with the average of the temperatures T.sub.2 and T.sub.3 being higher than the average of temperatures T.sub.o and T.sub.1. In such a case, three fluids are used, for example geothermal brine, ammonia, and fresh water with the invention being applicable both when T.sub.o &lt;T.sub.1 &lt;.sub.2 &lt;T.sub.3 and when T.sub.o &lt;T.sub.2 &lt;T.sub.1 &lt;T.sub.3.
An object of the present invention is to provide an exchange of heat between a plurality of predetermined heat-carrying circuits in the temperature range T.sub.o to T.sub.N. When the heat exchanges between the circuits are unbalanced, it is possible to re-establish balance by adding a minimum amount of complementary heat to the system with minimum work.
Another object of the present invention is to provide a method and apparatus for heat-exchange between a plurality of heat-carrying circuits at temperature levels ranging from T.sub.o to T.sub.N for the purpose of balancing the respective temperatures of the circuits while expanding a minimum of heat and of work.
An apparatus according to the present invention includes a plurality of compressor systems and turbine systems. Each compressor and turbine system operates within one of a plurality of bounded temperature intervals from T.sub.o to T.sub.1, T.sub.1 to T.sub.2, . . . , T.sub.N-1 to T.sub.N, covering the entire range from T.sub.o to T.sub.N.
Each compressor system includes a plurality of series-arranged stages with each stage having a compressor and a cell which is filled with a fluid, designated with transfer fluid. The transfer fluid is present in both liquid and vapor phases in each cell. In general, each cell further includes at least one calibrated orifice through which the transfer fluid arrives in liquid form from an adjacent stage of next higher rank and a liquid exhaust conduit communicating with an adjacent stage of next lower rank. In addition the cell has at least one vapor exhaust conduit communicating with the adjacent stage of next higher rank and a vapor inlet communicating through the stage compressor with the adjacent stage of next lower rank. All of the cells are ranked and arranged in series according to increasing vapor pressure (i.e. temperature). The cells may be crossed by one or more working fluid circuits. The working fluid circuit may carry temperature dependent heat and may pass serially through several successive stages. Other working fluid circuits may carry latent heat in a manner related to the particular stage under consideration. The first rank stage includes neither a compressor nor a liquid exhaust whereas the highest-rank stage includes neither a vapor outlet nor a liquid intake with associated orifice.
Each turbine system includes a plurality of serially arranged stages with each stage including a turbine, a pump and a cell. Each cell is filled with the transfer fluid in both liquid and vapor form and includes, in general, at least one orifice for receiving the vapor from an adjacent cell of next higher rank via the turbine, a liquid exhaust for evacuating the liquid by means of the pump towards the adjacent stage of next higher rank, and conduits for evacuating the vapor toward the adjacent stage of next lower rank and receiving liquid from the adjacent stage of next lower rank. The cells are arranged in series in the order of increasing vapor pressure and temperature, with the cells being crossed by the working fluid circuits both for temperature dependent heat and for latent heat. The first-rank stage includes neither a vapor outlet nor a liquid intake nor a pump, while the highest-ranking stage includes neither a vapor intake nor a liquid exhaust nor a turbine.
The compressor and turbine systems are mechanically and thermodynamically coupled together to form the overall apparatus, with communication being established between the atmospheres of the adjacent cells of two adjacent systems operating with the same working fluid. A thermodynamic equilibrium of the equipment is achieved by providing adjustable properties for at least one additional heat-exchanging circuit. The additional heat-exchanging circuit may include a valve and a heat exchange core which crosses at least one cell.
In addition, the mechanical coupling for the turbines and compressors of the equipment may include a motor for starting the apparatus and for supplying additional energy or for removing excess energy. In the apparatus, the cells of adjacent stages of two pluralities of stages of systems of different kinds may be joined so as to obtain a single cell per stage.